Posterior Mediastinal Lesions : A Short Review
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Posterior Mediastinal LesionsAlireza Kashani
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Mediastinal Compartments Posterior Mediastinum:
Also called paravertebral compartment
Defined by : Posterior Pericardium Anterior Spinal Ligament Superiorly: T4 vertebral
body Inferiorly: Diaphragm
Contains: Oesophagus, Descending
Aorta, Sympathetic Chain, Vagus Nerves, Thoracic Duct, Azygos and Hemiazygos veins, and Lymph Nodes
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Epidemiology Adults:
65% anterosuperior 10% middle 25% posterior compartments
Children: 25% anterosuperior 10% middle 65% in posterior compartments
Generally the incidence of posterior mediastinal lesions is higher in children.
50% are asymptomatic and are diagnosed incidentally
The absence of symptoms is generally is a clue to a benign lesion
Symptomatic lesions: Children: 60%-80% Adults: 50%-60%
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Diagnosis CT Scan is the diagnostic modality of choice and is superior to
even MRI in majority of the cases
MRI rarely indicated
Thoracic US is not helpful in posterior mediastinal lesions
Biopsy: is not necessary in majority of the cases and likelihood of a positive result parallels the presence of symptoms If needed:
CT-guided Thoracoscopic Limited posterolateral thoracotomy
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Neurogenic Tumours Young adults and children
They are the most common malignant neoplasm in children but they are less common than anterior mediastinal malignancies in adults. Lymphomas and Thymomas are more common in adults
Malignancy rate: Children: 50% Adults: 10%
They originate from embryonic neural crest cells around the spinal ganglia and from either sympathetic or parasympathetic components
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Neurogenic Tumours Source:
Intercostal nerve: Neurofibroma : benign
Of patients with nerve sheath tumours 25%-40% have multiple neurofibromatosis (von Recklingausen’s disease) and the incidence of malignancy is more common in these patient
Neurilemoma (Schwannoma) : Mostly benign but malignant schwannomas are rare The most common neurogenic tumor
Neurogenic Sarcoma (rare) Sympathetic Ganglia: can also have pheochromocytoma
Ganglioneuroma Ganglioneuroblastoma Neuroblastoma
Other: phrenic nerves, Vagus nerves
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Neurogenic Tumours Those with benign lesions are generally asymptomatic
Malignant tumors might present with symptoms such as: Spinal cord compression Cough Dyspnea Chest wall pain Hoarseness Rarely Horner’s syndrome
Rarely pheochromocytoma: Neuroblastoma or ganglioneuroma In all symptomatic patients, esp. those with significant hypertension it is
necessary to check for 24 h urine HVA (homovanillic acid) and VMA (vanillylmandelic acid)
If elevated then prior to operation to avoid adrenergic crisis: α-adrenergic blockers beta-blockers
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Neurogenic Tumours Intercostal nerves:
Neurofibroma Poorly encapsulated Random arrangement of spindle-shaped cells
Neurilemomas The most common neurogenic tumor Well-encapsulated Firm, gray-tan Two morphologic types:
Antoni’s type A: Organized architecture with a cellular palisading pattern of
growth Antoni’s type B:
Loose reticular pattern
Both of the above can happen as parts of neurofibromatosis type 1 (von Recklinghausen’s disease) and if left untreated can degenerate to neurosarcoma
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Neurofibroma
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Neurilemmoma – Mixed A and B
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Neurilemmoma – Antoni A
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Neurilemmoma – Antoni B
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Sympathetic Source
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Sympathetic Source Neuroblastic Tumors:
Arising from primitive sympathetic ganglia
Comprise: Neuroblastoma Ganglioneuroblastoma Ganglioneuroma
These differ in their degree of cellular and extracellular maturation Immature tumors:
Tend to be aggressive Occur in younger patients
(median age < 2) Mature tumors:
Older children (median age 7)
More benign Anywhere sympathetic nervous
tissue exists: Neck Posterior Mediastinum Adrenal Gland Retroperitoneum Pelvis
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Sympathetic Source Ganglioneuroma:
The most common neurogenic tumor occurring in children Benign Composed of gangliocytes and mature stroma Early age Located in the paravertebral region
Ganglioneuroblastoma: Composed of mature gangliocytes and immature neuroblasts Intermediate malignant potential
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Ganglioneuroma
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Ganglioneuroma
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Sympathetic Source Neuroblastoma:
Children < 4 y Small, round immature cells organized in rosette pattern Highly invasive Metastasized by the time the diagnosis is made:
Regional lymph nodes, bone, brain, liver, lung Some may have benign course Symptoms:
Cough, dysphagia, chest pain, and occasionally paraplegia Paraneoplastic:
Profuse watery diarrhea due to VIP Opsoclonus-Polymyoclonus syndrome Pheochromocytoma-like syndrome
Prognosis: Influenced by: DNA content, tumor proto-oncogenes, and catecholamine
synthesis The above aid in categorizing patients with neuroblastoma into low,
intermediate, and high-risk Rx: Resection +/- Chemotherapy
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Neuroblastoma
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Neuroblastoma
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Investigations CT:
Can help to identify the tumor and extent of involvement Those from peripheral nerves:
Well-defined, round or oval masses Noncalcified
Neurilemoma: Variable enhancement: homogenous or heterogenous On enhanced CT: variable attenuation
Neurofibroma: Usually homogenous Low-attenuation On enhanced CT: homogenous enhancement or with early central
blush Malignant nerve sheath tumors show variable attenuation
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Investigations CT:
Sympathetic Chain Tumors: Expand along the spinal axis No calcification or bone changes
Ganglioneuroma: Oblong homogenous low-attenuation lesions on both enhanced and
unenhanced CT Neuroblastoma:
Aggressive soft tissue lesions with calcification Ganglioneuroblastoma:
Mixed features of above Paragangliomas:
Appear in aortopulmonary window High contrast enhancement
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Investigations MRI: for dumbbell tumors
FNA
Tumor Markers: S-100
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Dumbbell Tumors Tumors of the posterior
mediastinum that extend into the spinal canal via the intervertebral foramen
It is necessary to identify these tumors to have a better planning, as inaccurate diagnosis would lead to intra-spinal hemorrhage and cord compression
MRI can identify these Smoothly rounded, homogenous
density abutting the vertebral column
Rarely present with cord
compression symptoms
They comprise 10% of patients with neurogenic tumors
Only 1-2% are malignant
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Management Standard of Care:
Surgical resection via thoracotomy or thoracoscopy Most of the neurogenic tumors can be resected via thoracoscopy; however,
malignant transformation, local invasion, and tumors larger than 5 cm increase the likelihood of conversion to thoracotomy
In most cases the tumor can easily be mobilized via thoracoscopy but any difficulty necessitates the conversion to thoracotomy
Resection of the nerve root is necessary in most of the cases A widened intervertebral foramen might be indicative of invasion of vertebral
canal (dumbbell tumor) and in these cases it is necessary to involve a neurosurgeon to assist in full resection of the tumor via a laminectomy in one stage procedure
Neuroblastoma: Spontaneous regression has been reported Stage:
I (noninvasive): Surgical resection alone II (locally invasive on same side of midline): Surgery + RTx III (invasive across the midline): Debulking + RTx + ChemoTx + Second-
look operation Children < 1 : good prognosis, prognosis has inverse correlation with age
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Oesophageal Masses These include:
Neoplasm Cysts Diverticula Hiatal Hernia Mega-oesophagus Oesophageal Varices
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Cysts Rare, benign, congenital
20% of all mediastinal lesions
Include: Bronchogenic Hydatid Enteric Intramural Oesophageal Neuroenteric Cysts
CT is the most effective modality of diagnosis
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Bronchogenic 60% of all mediastinal cysts
Location: Lung parenchyma Mediastinum
Histology: Ciliated columnar epithelium Cyst wall: cartilage, mucus
glands, smooth muscle Rarely communicate with the
tracheobronchial tree
Symptoms: Occasional compression on the
adjacent structures Recurrent infection Pain, Cough, Hemoptysis
Rx: If incidental finding in an
otherwise asymptomatic patient: observation is accepted
If symptomatic esp. if pain, cough, or hemoptysis the resection is strongly advised.
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Bronchogenic
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Bronchogenic
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Bronchogenic Dysphagia: as a result of
compression effect on the oesophagus
Presence of air-fluid level: suggests the possibility of communication with the tracheo-bronchial tree and increased chance of recurrent infections; hence, the possible need for resection
If it becomes infected, it is very likely that eradication is unsuccessful and it needs to be resected
Symptoms tend to develop with
time and hence the resection is advised in a healthy state before becoming symptomatic.
They can be resected via thoracoscopy or if in superior mediastinum via mediastinoscope.
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Bronchogenic
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Bronchogenic
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Gastroenteric Cysts Gastroenteric or duplication cysts:
peri-oesophageal lesions that arise from posterior division of the primitive foregut.
Features: Posterior or middle mediastinal mass Within or adjacent to the oesophageal
wall Communication with UGIT is
uncommon
Histology: Nonkeratinizing squamous, ciliated
columnar, gastric, or small intestinal epithelium
Epithelium is not a good differentiating feature from bronchogenic cysts: Presence of two muscular layers in
oesophageal cysts Cartilage and bronchial glands in
bronchogenic cysts
Usually asymptomatic, but symptoms: Resp: Cough, SOB, Recurrent
Pulmonary Infections, Chest Pain If gastric mucosa: perforation into the
oesophagus can cause haematemesis, or erosion into the adjacent lung can cause an abscess
Dx: EUS, Chest CT, Technetium Tc 99m (to identify gastric mucosa)
Rx: Resection: symptomatic, unclear cysts
– whether cystic or solid Observation: clearly cystic lesions,
otherwise asymptomatic
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Gastroenteric Cysts
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Gastroenteric Cysts
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Neuroenteric Cysts 5-10% of foregut lesions
Infants younger than 1
Connection to the meninges usually through a stalk
Associated with the congenital defects of the spine
Endodermal and ectodermal or neurogenic elements Failure of separation of the notochord from the primitive gut
CT evidence of mediastinal lesion with either of : Scoliosis, Hemivertebrae, Spina Bifida should prompt the possible Dx of neuroenteric cysts.
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Other Primary or metastatic lesions of
thoracic spine
Lymphomas : esp. Hodgekins
Infections such as TB
Post-traumatic haematoma
Descending thoracic aneurysm
Extramedullary hematopoiesis
Castleman’s Disease
Angiomyolipoma
Extralobar Pulmonary Sequestration
Neuroendocrine Carcinoma
Mediastinal Ependymoma
Cellular Hemangiomas
Melanotic Paraganglioma
Pancreatic Pseudocyst Mediastinal Extension
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Castleman’s Disease Giant lymph node hyperplasia
Vascular tumors surrounded by large LAP
Types : Localized: Hyaline Vascular,
Plasma Cell Generalized or Multicenteric
Hyaline Vascular: 90% of lesions Incidental finding in otherwise
asymptomatic Spinal cord compression has
also been reported Rx: Surgical excision, RTx is
ineffective
Plasma Cell:
More symptomatic: fever, fatigue, weight loss, hemolytic anemia, high ESR and hyper-γ- globulinemia as the result of the over production of IL-6
Resection is Rx of choice
Generalized: Histologic features of both of the
localized forms Older patients Symptoms:
Severe systemic symptoms Generalized LAP Hepatosplenomegaly
Mortality : 50% with median survival of 27 months and Progression to lymphoma
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Castleman’s Disease - Hyaline
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Castleman’s Disease - Plasma